THE ROLE OF CALCIUM IN ENDOTOXIN-INDUCED RELEASE OF CALCITONIN-GENE-RELATED PEPTIDE (CGRP) FROM RAT SPINAL-CORD

In the present study, the role of calcium in endotoxin-induced CGRP re lease was studied. 2.5-50 mu g/mL endotoxin and 1-10 mmol/L caffeine c aused concentration-dependent increase of CGRP release from rat spinal cord in vitro. However, no additive effect could be found when caffei ne and endotoxin were concomitantly incubated. By using capsaicin, Ca2 +-free medium, Omega-Conotoxin, nifedipine, W-7, ryanodine, MgCl2, Tri s-ATP, ruthenium red, the results indicate that the release of CGRP ev oked by endotoxin from the sensory fibers of rat spinal cord is depend ent on extracellular calcium. After entering into the cell through the N-type calcium channel, calcium binds to calmodulin, and triggers cal cium release from intracellular calcium store by activating the caffei ne-sensitive but ryanodine-insensitive mechanism.